The present invention relates generally to guns for mixing and discharging chemically reactive components adapted, upon mixing, to form a urethane or like insulating or protecting thermosetting plastic chemical foam, and more particularly, to a product mixing and dispensing gun having improved features providing ease of manufacturing, assembly, and maintanance, preferably through the use of low cost standard metal shapes.
In recent years, there has been a continuing increase in the consumption of foam products made by reactive chemical components. In particular, polyurethane foam materials are being used in ever increasing quantities in the areas of thermal insulation, flotation, coatings, and most recently, in the area of mass, and semi-mass production of specialty packages. A common application of resilient, low density, but relatively high load bearing urethane foams has been the specialty cushion packaging industry.
According to common practice, a corrugated, paperboard, or wooden shipping container is used to receive a relatively delicate product to be shipped by mail, freight, or other delivery service. Where the product is relatively delicate and expensive, and yet of considerable volume, perhaps a fraction of a cubic foot to several cubic feet or more in size, but is not mass produced to the extent that custom formed packaging is practical, it has been found desirable to package such products by a method which includes discharging pre-mixed but reacting urethane foam components into the container, placing a cover sheet over the reactants as they are polymerizing and the urethane is undergoing free rise expansion to its eventual height, placing the product to be packaged over the cover sheet as the foam continues to rise or has just finished rising, covering the product thus inserted into the package with another cover sheet and completing the package by surrounding the covered product with additional urethane foam, and permitting the remainder of the foam to expand to most or all of its final height before sealing the package.
In this manner, the expanding and reacting urethane foam assumes the contours of the product being packaged, and the product is completely and substantially evenly surrounded by a protective, shock absorbing cushion which also assumes the shape of the exterior container. This does away with the need for interfitting a product within intermediate packaging and then fitting such packaging to the shipping container. This method has proved very valuable for shipping medical and scientific instruments, electronic devices or various kinds, valuable artwork, china or other delicate objects, and a host of other products which would otherwise be readily susceptible to shipping and storage damage.
The advantages of these packaging systems are so great compared to many other packaging systems that there is a continuing increasing demand for the use of such systems.
According to present practices, the urethane components, a so-called resin or polyol component and a isocyanate component, are stored under high or ambient pressures in containers to which the discharge gun is attached by hoses. The materials are delivered to the mixing gun under high pressure from positive displacement pumps or other pumping means through the respective product hoses. Valves in the gun permit the products to flow through the hoses and into a mixing chamber, from which the products are mixed and dispensed under the control of a trigger operated discharge valve.
Since the components are mixed by direct or indirect impingement with each other under conditions of very high pressure to insure thorough mixing, the design of the discharge valves and nozzles has become a matter of concern in the art. Common designs include those featuring single or complex seals, means for lubricating and/or rinsing valve elements which are periodically exposed to the reactive components and the like. A chronic problem in the area of guns used for this purpose is that of periodically removing the nozzle either for cleaning or for replacement.
In the prior art, if the nozzle, which receives the products under high pressure is not properly located and seated, leakage or damage to the nozzle may result. In the past, fitting of the valve assembly to the gun has been a time consuming difficult and unreliable process.
According to the present invention, a gun is provided which has a valve assembly receiver and a product discharge valve assembly which are adapted to cooperate with each other and which may be readily and accurately secured together in a fast, foolproof manner. The product discharge valve assembly may be readily removed by hand without the use of tools, and misalignment between the inlet passages on the valve assembly and the outlet passages in the gun body is eliminated.
According to the present invention, the outlet and inlet ports respectively are aligned securely and positively by the combination of a V-groove self-centering arrangement on the receiver, a counterpart arrangement on the discharge valve assembly, and a cooperating alignment and locking stud unit. The discharge valve assembly includes a reciprocable valve having a stem portion which may include a quick-release lock arrangement for cooperation with the operating rod of the discharge gun, whereby the valve may be readily removed and replaced for maintenance or otherwise.
In view of the failure of the prior art to provide a foam discharge gun which provides ready and reliable removal and replacement of the discharge valve assembly, it is an object of the present invention to provide a gun having a valve assembly receiver and valve assembly adapted for easy and reliable installation and removal.
Another object of the invention is to provide a gun which has the advantages of prior art guns, but which has further advantages in use, including the ability to locate and lock a product discharge valve assembly within a counterpart receiver without the aid of tools and in a matter of few seconds or less.
Another object of the invention is to provide a so-called "pour gun" adapted to mix and dispense chemical products, which is easily serviceable for purposes of clearing the gun of chemical components, including reactive components, and of replacing components which become worn, clogged or damaged during use.
A further object of the invention is to provide a gun having a readily removable and replaceable discharge valve assembly which is compatible with the remaining elements of the gun, including an air operated free piston type actuator assembly.
A still further object of the invention is to provide a pour gun for mixing and discharging reactive chemicals, which gun has various mating surfaces which are easy to machine and finish, and which may be manufactured without the use of expensive tooling, and making use of common readily available inexpensive prefabricated shapes such as bar stock.
Yet another object of the invention is to provide a discharge valve assembly for a chemical product mixing and dispensing gun wherein the discharge valve assembly within the receiver of the gun is virtually incapable of misalignment, and which will seat equally well within a wide range of component tolerances.
Another object of the invention is to provide a valve assembly which includes a reliable seal and packing assembly to insure against leakage or clogging of the mixing and discharging valve assembly in the use of the gun.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a gun which includes a handle and trigger, a pneumatically actuated free piston valve operating system, and a receiver adapted to receive a discharge valve assembly, with the receiver and the discharge valve assembly each including cooperative, flat side wall portions forming parallel sided V-shaped locating and locking surfaces, with a positioning and locking member adapted to cooperate further therewith for applying a locking force in the direction of the V-groove apex, and preferably with the discharge valve assembly including a fluorocarbon seat and a reciprocable flow control valve therein.
The exact manner in which the foregoing objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example, and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.